Not all code paths return a value?

I'm getting an error in Unity that I've never gotten before. It says:

Assets/Scripts/Managers/PlayerFunds.cs(20,22): error CS0161: `PlayerFunds.SaveCredits()': not all code paths return a value

The script I'm writing is very simple so I don't understant what the problem may be. Here is the code:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerFunds : MonoBehaviour {
     public int playerCredits;
 
 
     void Start() {
         playerCredits = PlayerPrefs.GetInt("Credits");
     }
 
     public void AddCredits(int amount) {
         playerCredits += amount;
     }
 
     public void SubtractCredits(int amount) {
         playerCredits -= amount;
     }
 
     public float SaveCredits() {
         PlayerPrefs.SetInt("Credits", playerCredits);
     }
 }